This invention relates to missile tracking and guidance systems in general and in particular to tracking and guidance systems which do not require transmission of energy toward the intended target.
Missile tracking and guidance systems are well known in the prior art. Generally such systems fall into two broad categories of systems. "Active" systems are those guidance systems which require the transmission of laser, radar or radio frequency energy at the intended target. Examples of such active systems abound and include missiles which incorporate an entire radar system which acquires and tracks a target during missile flight. A second example of the active system includes a known system in which a laser beam projection device is utilized to "paint" the target and identify that target to the missile guidance system. These known active guidance systems are accurate and reliable; however, the transmission of some form of energy at the target has the effect of alerting the target to the presence of a missile and may in fact generate sufficient warning to the target as to enable some form of countermeasure or evasive action.
Those skilled in the art will appreciate that these active guidance and tracking systems are well suited to guiding a missile toward a nonintelligent target; however, in the event that an intelligent target is selected (i.e. a manned aircraft) such systems are not the systems of choice in view of the possible reaction of the target to reception of the energy transmission necessary to guide the missile.
A second large category of missile guidance and tracking systems are the so-called "passive" guidance systems. These guidance systems are referred to as passive because they do not transmit energy at the target which can be detected. One example of such a passive guidance system is an infrared or heat-seeking system which acquires and tracks the jet exhaust of a target missile or aircraft. This type of tracking system has been utilized with excellent results; however, it does suffer from being "nondiscriminatory" in nature. That is, the heat-seeking system will acquire and track the hottest heat source within its field of regard. It is therefore possible to evade such systems by deploying a small drone heat source or by flying a track which will intersect the track of alternate heat sources (i.e. the launching aircraft).
A second form of passive tracking and guidance systems incorporate a system which homes in on the radar and radio transmission of the target. These systems are sometimes utilized in conjunction with an active radar guidance system and will home in on an interference transmission if its radar reception is hindered. Again, this system is nondiscriminatory and can be defeated by maintaining a low profile electromagnetically or by the utilization of electronic countermeasures which can alter the apparent position of the source of a transmission.